Temporally modulated multi-LED for enhanced subconscious physiological responses

ABSTRACT

A light source and a method of generating a light using the light source is disclosed. The light source is configured to produce a plurality of distinct colors in generating the light, one of the distinct colors falling within a blue spectral light band. A light controller modulates the spectral light produced by the plurality of distinct colors. The modulation provides melanopsin contrast in order to increase melanopsin responsiveness of a subject exposed to the generated light and maintains the color temperature, color quality, and color constancy experienced by the subject in a lit viewing environment within an acceptable range.

CROSS-REFERENCE TO RELATED APPLICATION

The priority benefit of U.S. Provisional Patent Application No.62/365,610, filed Jul. 22, 2016, and entitled “Temporally ModulatedMulti-LED for Enhanced Subconscious Physiological Responses” is claimedand the entire contents thereof are incorporated by reference herein.

STATEMENT OF GOVERNMENT SUPPORT

This invention was made with government support under grant numbersEY013934 and EY007003 awarded by the National Institutes of Health. Thegovernment has certain rights in this invention.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Photic stimulation of retinal neurons evokes not only conscious visionbut also subconscious responses central to our well-being. Because theaverage person spends >80% of their time indoors, the quality ofartificial light has far-reaching health impacts. To date, lightingtechnologies have been designed to improve energy efficiency and visualcomfort, but their physiological effects have been largely overlooked.Because the recommended illuminance of indoor lighting is typically≥10-fold lower than outdoor levels, inadequate daytime light exposurehas been linked to various morbidities.

The health impacts of light have been a topic of renewed interestrecently, partly due to the recent discovery of a new class ofphotoreceptors: intrinsically photosensitive retinal ganglion cells(ipRGCs). ipRGCs sense light using the photopigment melanopsin which ismost sensitive to 480 nm blue light. ipRGCs are the primary neuronsmediating non-image-forming physiological responses to light, e.g., thepupillary light reflex, suppression of nocturnal melatonin release, andentrainment of circadian rhythms such as sleep to the light/dark cycle.As researchers are learning, insufficient daytime light exposure oroverexposure during subjective night can result in not only discomfortbut also jet lag symptoms, seasonal affective disorder (SAD), andgeneral depressive disorders. Conversely, boosting daytime blue lightexposure can decrease reaction times, increase alertness, and ameliorateSAD symptoms. But, as researchers are finding, it is unrealistic topromote subconscious photostimulation simply by enhancing blue emissionin indoor lighting as that would cause poor color rendering andundesirable color temperature. Thus, having an alternative strategy tomake indoor light more potent for subconscious visual stimulation wouldbe highly advantageous.

SUMMARY OF THE INVENTION

Light is essential for not only visual perception but also the properregulation of circadian rhythms, alertness and mood. These subconscious,non-image-forming visual responses are mediated by intrinsicallyphotosensitive retinal ganglion cells (ipRGCs), which use thephotopigment melanopsin to sense light. Pulsing light has been shown toreduce photoreceptor adaptation and therefore elicit strongernon-image-forming responses than constant light of comparable energydensity.

The present techniques propose a new paradigm for general lighting thatenhances subconscious visual stimulation, by introducing amelanopsin-selective flicker into the light through a silentsubstitution technique, which minimizes cone-based perception of theflicker.

In some examples, the techniques use a linear optimization algorithm,although numerous other mathematical optimization frameworks can beemployed. The algorithm maximizes contrast of the subconscious,melanopsin-based response function while keeping conscious, cone drivenresponses to the pulsing light fixed. Additional boundary conditionsutilize the lighting industry's standard test color samples (TCS) as anenvironmental mimic, as well as any specified object color, in order tolimit the amount of perceived color change caused by the pulsing lightwithin the viewing environment. For purposes of this application, theterm “perceived color” refers to color temperature and brightness orluminosity, as well as other possible light qualities. With the presenttechniques, newly generated light can help overcome the detrimentaleffects of insufficient daytime light such as depression and sleepdisorders.

In accordance with an example, a method of generating light using alight source comprises: generating lighting signals for controlling thelight source, wherein the light source is configured to produce aplurality of distinct colors in generating the light, one of thedistinct colors falling within a blue spectral light band; modulatingthe lighting signals to modulate the light produced by the plurality ofdistinct colors, the modulation being chosen to provide optimalmelanopsin contrast in order to increase melanopsin responsiveness of asubject exposed to the light and the modulation being chosen to maintaincolor temperature and color quality within an acceptable range; andapplying the modulated lighting signals to the light source andgenerating the light for increasing the melanopsin contrastresponsiveness of the subject exposed to the light.

In accordance with another example, a light source comprises: aplurality of light source elements, each producing an output light at adifferent wavelength in the visible spectrum; and a light controlleradapted to modulate one or more of the plurality of the light sourceelements, wherein the modulation increases melanopsin contrastresponsiveness of a subject exposed to the generated light and themodulation maintains, within an acceptable range, color fidelity fromthe overall light output from the light source as experienced by asubject.

In accordance with another example, a method of adapting a pulsed lightfor general illumination comprises: providing a plurality of LEDchannels each generating light, the LED channels including at least fourdistinctly colored LEDs; setting a first light mode at a first spectrumto maximally stimulate melanopsin responsiveness of a subject, the firstspectrum being formed by light from the at least four distinctly coloredLEDs, the first light mode comprising a light intensity that maximizesmelanopsin contrast responsiveness and a blue light intensity, a redlight intensity, and/or a green light intensity that define a colortemperature and brightness of the first light mode; setting a secondlight mode at a second spectrum to more weakly stimulate melanopsinresponsiveness of the subject compared to the first light mode, thesecond spectrum being formed by light from the at least four distinctlycolored LEDs, the second light mode comprising a light intensity thatmore weakly stimulates melanopsin responsiveness and a blue lightintensity, red light intensity, and/or a green light intensity thatdefine a color temperature and brightness of the second light mode;setting the color temperature and brightness of the first light mode tomatch the color temperature and brightness of the second light mode; andmodulating between the first light mode and the second light mode tostimulate the subject while maintaining an optimized melanopsin contrastbetween the first light mode and the second light mode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-C provide comparisons of human pupillary responses toflickering versus steady lights with black columns illustrating optimalflicker responses at three photon counts: 13.7 log photons cm⁻² (FIG.1A), 14.7 log photons cm⁻² (FIG. 1B), and 15.7 log photons cm⁻² (FIG.1C).

FIGS. 2A-B illustrate responses to prolonged photostimulation resultingfrom exposure to a 12.3 log photons cm⁻² constant light (FIG. 2A) or a13.3 log photons cm⁻² s⁻¹ stimulus flickering at 2 Hz with a 12% dutycycle (FIG. 2B).

FIGS. 3A-C illustrate responses of mouse ipRGCs to flickering versussteady lights with the stimuli presented shown in FIG. 3A,representative responses from an M1 cell and an M2 cell shown in FIGS.3B1 and 3B2 respectively, and data averaged from all cells shown in FIG.3C.

FIG. 4 illustrates spikes induced by twenty 1-s light pulses presentedto rat ipRGCs during rod/cone signaling block at five intervals: 0 s(i.e. steady light), 1 s (0.5 Hz), 5 s (0.17 Hz), 14 s (0.07 Hz) and 29s (0.03 Hz).

FIG. 5 illustrates a proposed scheme to incorporate a pulsed blue lightin a white light source for general illumination.

FIG. 6 illustrates suggested chromaticities to be explored as candidatelighting color specifications fall along the Planckian locus and itsisotemperature lines from 3000 to 10000 K in small intervals as well asnear and around the equi-energy point.

FIGS. 7A-I illustrate trends in melanopsin contrast with relaxation ofcone response constraints for a light with specified system parameters,with FIGS. 7A-7D illustrating responses to a system consisting of 5 LEDsand FIGS. 7E-7I illustrating melanopsin Michelson contrasts forsimulations with 4, 5, 6, 10, and 400 LED channels, respectively.

FIGS. 8A-F illustrate spectra and metrics for general and therapeuticlighting with FIGS. 8A and 8B illustrating spectra of two example lightsources for general lighting (FIG. 8A) and therapeutic lighting (FIG.8B), FIGS. 8C and 8D illustrating individual CII values for 14 TCSsspecified in CRI calculations for the general (FIG. 8C) and therapeutic(FIG. 8D) light sources, and FIGS. 8E and 8F illustrating the amount ofcone response change to the first 8 TCSs, as spectra oscillate betweenthe maximum- and minimum-melanopsin states for general (FIG. 8E) andtherapeutic (FIG. 8F) lights.

FIG. 9 provides values of key lighting parameters for the general andtherapeutic lights shown in FIGS. 8A,B.

FIGS. 10A-10E illustrate mean CII vs. melanopsin contrast as TCSboundary conditions are expanded for lights with 4, 5, 6, 10, and 400independent LED channels, respectively.

FIG. 11 illustrates electroencephalograms (EEGs) that were recorded fromtwo subjects (GV and KW) using two scalp electrodes (Fz and Cz), whileeach person was viewing the 5-LED light source presenting 6 differentstimuli.

FIG. 12 shows the results from a computer-based cognitive performancetest.

FIG. 13 illustrates a processing system for generating light modulationmodels and controlling light output to produce dynamic light, inaccordance with examples described above.

FIG. 14 illustrates an example implementation of the generated lightmodel in an LED light formed of an LED array.

FIG. 15 is an example of a flat panel display device having two LEDselectrically connected to a light controller providing modulating lightsignal controls to the LEDs, and with a diffuser panel for evenlyemitting light.

FIG. 16 is an example of an Edisonian lighting configuration in whichtwo LEDs electrically connected to a light controller providingmodulating light signal controls to the LEDs, are housed within a lightbulb shaped housing and in which a diffuser panel is shown.

FIG. 17 provides an exemplary method for adapting a pulsed blue lightfor general illumination.

DETAILED DESCRIPTION

A detailed description of each of the figures and tables is providedfirst below, followed by a more general discussion of the relevantdisclosure of this application. FIGS. 1-4 summarize empirical evidencethat temporally flickering light stimulates ipRGCs more strongly thansteady light. FIGS. 1A-C provide comparisons of human pupillaryresponses to flickering versus steady lights. The black columnsillustrate optimal flicker responses at three photon counts: 13.7 logphotons cm⁻² (FIG. 1A), 14.7 log photons cm⁻² (FIG. 1B), and 15.7 logphotons cm⁻² (FIG. 1C). These flicker responses are compared withresponses to steady lights that have either the same photon counts asthe optimal flickers (hashed columns) or higher photon counts (graycolumns). *P<0.05. ***P<0.001. Five subjects participated, eachcontributing two trials to all 14 conditions.

FIGS. 2A-B illustrate responses to prolonged photostimulation. After 60minutes of dark adaptation, a subject was exposed to 60 minutes ofeither a 12.3 log photons cm⁻² constant light (as shown in FIG. 2A) or a13.3 log photons cm⁻² s⁻¹ stimulus flickering at 2 Hz with a 12% dutycycle (as shown in FIG. 2B). In both cases, a total of 15.9 log photonscm⁻² was delivered per trial. Each trace was generated by averagingthree trials. The steady-state pupillary response to the flicker (FIG.2B) was significantly greater than that to the steady light (FIG. 2A).

FIGS. 3A-C illustrate responses of mouse ipRGCs to flickering versussteady lights. Whole-cell current clamp recordings were made from 11mouse ipRGCs (seven M1 cells and four M2 cells) under conditions thatpreserved synaptic input. Two stimuli (shown in FIG. 3A) were presentedto each cell, in random order: a 12.9 log photons cm⁻² s⁻¹ lightflickering at 2 Hz with a 10% duty cycle, and a steady 11.9 log photonscm⁻² s⁻¹ light with the same photon count as the flicker. All stimuliwere full-field 440-nm light. Representative responses from an M1 cellare shown in FIG. 3B1 and representative responses from an M2 cell areshown in FIG. 3B2. The insets show magnified views of the final 5seconds of the responses. FIG. 3C shows data averaged from all cells,illustrating that both ipRGC types displayed larger steady-state spikingresponses to the flicker. *P<0.05. **P<0.01.

FIG. 4 depicts the results when twenty 1-s light pulses were presentedto rat ipRGCs during rod/cone signaling block at five intervals: 0 s(i.e. steady light), 1 s (0.5 Hz), 5 s (0.17 Hz), 14 s (0.07 Hz) and 29s (0.03 Hz). The 0.07 Hz flicker induced the most spikes, indicatingthat melanopsin responded more strongly to this flicker frequency thanthe steady light or the other three flicker frequencies.

FIGS. 5-10E summarize mathematical evidence that multi-LED lightscontaining melanopsin-targeted oscillations do not significantly distorthuman color vision. FIG. 5 illustrates a proposed scheme to incorporatea pulsed blue light in a white light source for general illumination.Since human beings see color using 3 distinct color-encodingphotoreceptors (known as cones), it is possible to produce an infinitecombination of 3 distinct color sources that when mixed appear to be thesame color. As demonstrated in FIG. 5, two sets of distinct colors canappear to be the same (i.e. they are metamers) when optically mixed.

FIG. 6 illustrates suggested chromaticities to be explored as candidatelighting color specifications fall along the Planckian locus and itsisotemperature lines from 3000 to 10000 K in small intervals-100 Kintervals in the figure—as well as near and around the equi-energypoint, i.e. a square bounded by (0.3203,0.3203) and (0.3403,0.3403).Sampled points are plotted here using the 10° response functions of the1964 supplemental observer.

FIG. 7 illustrates survey of trends in melanopsin contrast withrelaxation of cone response constraints for a light with specifiedsystem parameters. In FIGS. 7A-7D, the system consists of 5 LEDs (peakwavelengths 456, 488, 540, 592 and 632 nm; 10 nm full width at halfmaximum) with color coordinates along the Planckian locus, and the coneresponse change is calculated with respect to the oscillation of whitelight between the maximum-melanopsin spectra and minimum-melanopsinspectra. When calculating cone response changes in this case, the first8 TCSs from the CRI standards are used. The tolerance to change in coneresponse ranges from 0% to 200%. As tolerance is increased, theoptimized melanopsin contrast increases with mean cone response changesincreasing concomitantly (FIG. 7A), ultimately matching theunconstrained contrast as tolerance approaches 200% (FIG. 7B). However,CII also increases as tolerance goes up (FIG. 7C). Melanopsin contrastreaches a maximum at 7000 K correlated color temperature (FIG. 7D).FIGS. 7E-7I illustrate melanopsin Michelson contrasts for simulationswith 4, 5, 6, 10, and 400 LED channels, respectively, plotted on the CIEchromaticity diagram using 10° cone fundamentals. The correlated colortemperature of maximum contrast shifts when the number of independentLED channels is adjusted. In FIGS. 7D-7I, isotemperature results arepresented, as seen by the 3 contour-matched scatter plot groupings ineach panel.

FIG. 8 provides spectra and metrics for general and therapeuticlighting. FIGS. 8A and 8B illustrate spectra of two example lightsources with different applications: general lighting (FIG. 8A) andtherapeutic lighting (FIG. 8B). FIGS. 8C and 8D illustrate individualCII values for 14 TCSs specified in CRI calculations for the general(FIG. 8C) and therapeutic (FIG. 8D) light sources. FIGS. 8E and 8Fillustrate the amount of cone response change to the first 8 TCSs, asspectra oscillate between the maximum- and minimum-melanopsin states forgeneral (FIG. 8E) and therapeutic (FIG. 8F) lights.

FIG. 9 provides values of key lighting parameters for the general andtherapeutic lights shown in FIG. 3. “CCT”: the correlated colortemperature of the illuminant. “Max/min ratio”, the ratio of themelanopsin response induced by the maximum- vs. the minimum-melanopsinspectrum. “Mean CII”, the average color inconstancy index with respectto all 14 TCSs. “CRI min”, “CRI max”, “CQS min” and “CQS max”, the colorrendering index and color quality scale values of the minimum- andmaximum-melanopsin illuminants.

FIGS. 10A-10E illustrate mean CII vs. melanopsin contrast as TCSboundary conditions are expanded for lights with 4, 5, 6, 10, and 400independent LED channels, respectively. TCS 9-12 are high chroma red,yellow, green, and blue colors respectively, which are excluded from thecalculation of general CRIs but are regularly encountered in real life.In the legend, “first 8” refers to the inclusion of the first 8 TCSs inthe constraint matrix, “first 8+9th” means including the first 8 TCSsplus the 9th TCS, etc. The panels reveal trends toward reduced CII andcontrast as additional TCSs are included in the constraints. IncludingTCS 12 (strong blue) in the boundary conditions shows the largest dropin melanopsin contrast, often with little benefit to reduction in meanCII.

FIG. 11 and FIG. 12 summarize empirical evidence that multi-LED lightscontaining melanopsin-targeted oscillations enhance alertness andcognitive performance in humans. In FIG. 11, electroencephalograms(EEGs) were recorded from two subjects (GV and KW) using two scalpelectrodes (Fz and Cz), while each person was viewing the 5-LED lightsource presenting 6 different stimuli. “Min”: a steadyminimum-melanopsin stimulus designed to excite melanopsin weakly. “Max”:a steady maximum-melanopsin stimulus that excites melanopsin strongly.“0.01 Hz”, “0.1 Hz”, “0.5 Hz” and “2.5 Hz”: melanopsin-isolating stimulithat oscillate sinusoidally between the min and max states at the statedfrequencies. “Darkness”: the light was turned completely off. Areduction in low alpha power indicates an increase in alertness.

FIG. 12 shows the results from a computer-based cognitive performancetest. This experiment was performed on three subjects, who were randomlyselected students. In each session, a subject was comfortably seatedwhile reading a book for 1 hour under either the melanopsin-selectiveoscillating light, the minimum-melanopsin steady light, or themaximum-melanopsin steady light. The subjects were not told the expectedeffects of the lighting conditions. In total, the subjects were testedunder the oscillating light 10 times and the steady lights 12 times. Thedata from all subjects were averaged and the oscillating light was foundto be superior to the steady lights in all three parameters measured:reaction time, distractability, and error rate.

The last five figures present example strategies to implement themulti-LED lighting technology disclosed herein, as discussed in greaterdetail below after a broader discussion of the disclosure of the presentapplication.

Temporally modulated light stimulates the subconscious visual systemmore effectively than constant light. For both ipRGCs and downstreamtargets such as the central circadian pacemaker, melanopsin-basedresponses to constant light adapt within seconds. Thus, anintermittently varying light intensity reduces melanopsin adaptation andenhances ipRGC responses, ultimately stimulating cognitive brainactivity.

In a human study, we systematically tested many light flickers ofdifferent intensities, duty cycles and flicker frequencies, as well asmany steady light stimuli of various intensities, and found that theoptimal flickers always caused greater pupil constrictions than steadylights containing the same total number of photons, as shown in FIGS. 1and 2. Remarkably, even when the intensities of the steady lights wereincreased by up to 10-fold, these optimal flickers still caused greatersteady-state pupil constrictions, as summarized in FIG. 1. Because priorprimate research had demonstrated a tight correlation between thepupillary light reflex and ipRGC spiking activity such that a higheripRGC spike rate leads to a greater pupil constriction, we can inferfrom the FIG. 1 and FIG. 2 results that flickering light is far moreeffective than constant light for stimulating human ipRGCs. Confirmingthis result, electrophysiological recordings from individual mouseipRGCs showed that flickering light induces more action potentials (alsoknown as “spikes” or “impulses”) than steady light containing the samephoton count, as summarized in FIG. 3. This trend was observed in bothM1 and M2 types of mouse ipRGCs, which are analogous to the two types ofipRGCs present in the human retina.

The above experiments were conducted under conditions preservingrod/cone input to ipRGCs, i.e. ipRGCs responded to light not onlydirectly via melanopsin but also indirectly via the rod and conephotoreceptors. In the experiment shown in FIG. 4, we made spikerecordings from individual rat ipRGCs under pharmacological conditionsthat blocked rod/cone signaling, so that melanopsin-based lightresponses could be measured in isolation. Twenty 1-s light pulses werepresented at five intervals: 0 s (i.e. steady light), 1 s (0.5 Hz), 5 s(0.17 Hz), 14 s (0.07 Hz) and 29 s (0.03 Hz). All four flickers evokedmore spikes than the steady light, indicating that melanopsin respondsbetter to flickering light than steady light. Moreover, the 0.07 Hzflicker induced more spikes than the other three flicker frequencies,suggesting that the best frequency for stimulating melanopsin is between˜0.05 and ˜0.15 Hz.

Given that melanopsin is most sensitive to blue light and that ipRGCsrespond better to flickering light than to steady light, one way ofmaking daytime interior lighting healthier is by incorporatingtemporally modulated blue light into electric lights. However, thishypothetical light source is not practical because of the presence of astrong blue hue and because periodic fluctuation would create a veryunpleasant visual experience. Thus, we developed a novel lightingtechnology incorporating a technique called silent substitution tocreate a blue light that flickers subconsciously. In this technique, thespectral contents of light are shifted in such a coordinated way thatthe shift selectively changes the activity of just one photopigmentwhile leaving all other photopigments unaffected.

In some examples, the present techniques include using a light sourcehaving 4 differently colored LED channels: a blue channel tuned tomelanopsin's peak sensitivity, and 3 additional channels with shorterand longer wavelengths. The non-blue channels offset the blue channel tocreate a visually appealing warm white appearance, and the 4 channelsare modulated according to the silent substitution method so that thetemporal fluctuation is detected only by ipRGCs' subconsciousphotopigment melanopsin but not by cone or rod photoreceptors; thus, thelight is perceived by the viewer as a steady light.

In some examples, the present techniques include using a light sourcehaving 4 differently colored LED channels such as that depicted in FIG.5: a first blue channel tuned to melanopsin's peak sensitivity (i.e., ator near 480 nm), a second spectrally non-redundant blue channel tuned toa wavelength triggering a weaker melanopsin response (i.e., farther from480 nm), a green channel and a red channel. The two blue channels areturned on alternately. The intensities of the green and red channels aretemporally modulated to compensate for the differences of the two bluechannels. That is, the spectrum of the white light output is oscillatedbetween two spectral states, one maximally and one minimally stimulatingmelanopsin. The four channels are modulated according to the silentsubstitution method so that the temporal fluctuation is detected only byipRGCs' subconscious photopigment melanopsin but not by cone or rodphotoreceptors, so that the light is perceived by the viewer as a steadylight.

The present techniques incorporate temporally modulated blue light intoan electric light thereby boosting subconscious responses at a typicalindoor illuminance level. However, a proper compensation scheme isneeded to mask the periodic intensity fluctuation. When temporallymodulating the blue component in a white light, two sources of perceivedfluctuation are generated: temporal variations in the color coordinatesof the light source itself and scenery variations of the illuminatedenvironment. With the present techniques, we show that by using multipleindependently modulated color channels, the silent substitutiontechnique, and mathematical optimizations, the sources of visibleflickering can be minimized, while maintaining the beneficial effectsfor ipRGC targets.

Since conscious vision is primarily mediated by cone photoreceptorsunder daytime lighting conditions, two stimuli with dissimilar spectralpower distributions can still look identical to an observer if bothspectra produce equivalent responses among the 3 cone channels. Suchspectra are called cone metamers. When one metamer is substituted withanother, no change in the cone response is evoked; this process iscalled silent substitution.

The present techniques extend the metamer concept and introduce four ormore color channels implemented using light sources, such as LEDs. Whenthe channel that most strongly stimulates melanopsin is temporallymodulated, the other channels are simultaneously modulated such that theoverall cone-based color coordinates remain constant. In this way, theproposed light source may periodically oscillate between two conemetamers: one that stimulates melanopsin the most (“maximum melanopsin”)and another that stimulates it the least (“minimum melanopsin”). Tominimize the environmental flickering, we searched within the “maximummelanopsin” and “minimum melanopsin” solutions such that the pair ofspectra generates the least spectral reflection shifts from standardizedtest color samples (TCS).

In confirming our results, the shift in cone excitation was calculatedas a Weber contrast (i) for each TCS and (ii) for each of the 3 coneresponses (short-, mid- and long-wavelength), by integrating the maximummelanopsin spectrum with the cone responses and taking the differencefrom the value for the minimum melanopsin spectrum.

To further measure the perceived shift in color when alternating betweenthe two spectra, a color inconstancy index (CII) was applied for eachTCS and averaged. Here we used the CIE color difference equation (2000),CIEDE2000.

Color inconstancy is typically calculated to gauge the degree of colorfidelity of a color sample with a change in illuminant. In this case, weestimated the inconstancy of the scene as the lighting spectrumoscillates between the minimum and maximum melanopsin spectra.

To calculate the CII, we first applied a chromatic adaptation transformfor both minimum and maximum melanopsin spectra with respect to thereference illuminant best suited for use with CIEDE2000. Since thisdifference equation operates on the basis of CIELAB, the referenceilluminant is D65 with an illuminance level of 1000 lux. The adaptationtransform was used for the index to correlate with visual evaluation.The selected transform was CAT02 with sharpened cone fundamentals; it isthe most recent recommendation from CIE and can be found in the CIECAM02specifications.

The TCS spectral reflectances were integrated with the spectral profileof first the minimum-melanopsin and then the maximum-melanopsinilluminant and tristimulus values were calculated. The transform wasapplied in order to calculate corresponding color coordinates for TCSreflectances under the reference illuminant. Once the correspondingcolor coordinates under the reference illuminant were specified for aTCS under minimum- and maximum-melanopsin conditions, a CII wascalculated.

The number of color channels, e.g., the number of LED channels can vary.We discuss herein specific examples of 4 LED channels and 5 LEDchannels. However, any number of color channels may be used withcorresponding increases in the controller operation when determiningcolor separation and minimum-melanopsin and maximum-melanopsinresponses.

In examining sample optimum conditions, we varied the number of LEDchannels from 4 to 400 and the spectral full width at half maximum(FWHM) from 1 nm to 100 nm. We also varied the maximum allowable shiftin cone response between the maximum and minimum melanopsin spectra. Asmall tolerance in the cone shift was used for the light source to besuitable for general illumination (FIG. 8A), whereas this constraint canbe greatly relaxed for a therapeutic light source (FIG. 8B).

In these examples, we considered white light sources along the Planckianlocus and its isotemperature lines with color temperatures ranging from3000 to 11000 K in 100 K intervals (FIG. 6). For each condition, wecalculated the color rendering index (CRI), color quality scale (CQS),and CII. The CII value provided an approximate quantity for predicting“just noticeable differences” in color. A CII of 1 describes a barelyperceptible color difference in side-by-side sample comparisons by anaverage viewer, while larger values reflect greater, more readilyperceived color differences. FIG. 7 summarizes the results for anilluminant system containing 5 LEDs, each with a 10 nm FWHM. Tofacilitate discussions, we focus on three tolerance levels in FIG. 8: noconstraints, 50% tolerance, and 5% tolerance. The first case is relevantto phototherapeutic devices while the others have potential applicationsin general lighting.

We found that there is a tradeoff between melanopsin contrast andilluminant quality measured by CRI (or CQS) and CII. As expected, thehighest melanopsin contrast can be obtained when there is no constrainton the tolerable cone response shift between the two spectra. When themaximum number (400) of LED channels was used for example, the highestmelanopsin contrast was achieved: a Michelson contrast of 87.4%,corresponding to a maximum-to-minimum melanopsin response ratio of 14.9.However, this system also produced the lowest (poorest) CRI and CQSvalues: the CRI of the maximum and minimum spectra oscillates between−26 and −306, and the CQS value is 0 for both spectra. The mean CII is34, which will produce an obviously fluctuating and hence unpleasantlighting environment. In short, the melanopsin effect can be maximized,but designers should also consider the effect on color rending of theresulting affected light.

In other tests, we examined for the smallest CRI shift, noting that manyconditions from our iteration qualify with little change in CRI value.These conditions can also demonstrate high melanopsin contrasts. Forexample, a 6-LED system with a tolerance of ±50% and FWHM of 10 nm has acontrast of 47%. However, CRI values for such as system can be very low,in this case 33, with CII at 16 and CQS oscillating between 9 and 32.

The illuminant in FIG. 8B contains 4 LEDs with chromaticity coordinates(0.4370,0.4042), corresponding to a CCT of ˜3200 K. Its melanopsincontrast is 30.1%, and its maximum-to-minimum melanopsin response ratiois 1.86. The CRI values of its minimum and maximum spectra are 65 and80. Its CQS values are poorer and range from 37 to 68, and the mean CIIfor 14 TCSs is 8.2. The CII for TCS 12 is 26.7, more than twice thesecond largest value of 12.0, for TCS 10 (FIG. 8D).

In examining TCSs, we applied a TCS constraint matrix to mimic changesin the appearance of a simulated environment as the light oscillatesfrom the minimum- melanopsin spectrum to maximum-melanopsin spectrum.The TCS constraint matrix was used to limit the amount of change thatoccurs to the cones in the eyes of a subject, if the subject were to belooking at a colored object under the modulated light herein. TCS refersto test color samples that were chosen as commonly representativesamples of colored objects we might encounter in our rooms. The TCSswhere chosen because they represent the colors highly encountered in thelighting practice for calculating CRI, which is one of the mostimportant lighting metrics. With the constraint matrix, we were able tospecify that, when looking at a TCS, we can only allow our coneresponses to change a certain amount, while the algorithm of thetechniques herein calculates the optimum melanopsin contrast or optimumrange for melanopsin contrast per the TCS matrix value constraints.

However, for viewers suffering SAD or other conditions arising from pooripRGC stimulation, the therapeutic benefits of a high melanopsincontrast might take priority over color inconstancy, i.e., theseindividuals may be willing to tolerate subtle changes in the shades ofobjects in exchange for better therapeutic effects from their interiorlighting. It is believed that these subtle shifts can be reduced byusing a light source that alternates between the maximum and minimumspectra in a smooth, sinusoidal fashion. Whereas existing lighttherapies (which use intense steady light) are inefficient and requireprolonged dedicated viewing, incorporating phototherapy into generallighting would circumvent such inconvenience, allowing users to receivetherapy while engaging in normal daily activities.

A small tolerance in visual shift usually leads to a low CII. Incombination with a large FWHM, the light source can produce a moderatemelanopsin contrast with hard-to-notice oscillation. Recent in vitrorecordings suggested that the optimal modulation frequency formelanopsin-based photoresponses in rat ipRGCs was ˜0.1 Hz (FIG. 4).Hence even with the worst case scenario, such as a room dominated by thecolor similar to TCS 12 (deep blue), the change generated by a lightsource oscillating sinusoidally at ˜0.1 Hz will be slow and likelybarely noticeable. For example, a 4-LED system with a 100 nm FWHM (FIG.8A) yields a high CRI of 92. The CII mean for all TCSs is 1.6 (FIG. 8C).This system has a melanopsin contrast of 4.2%. A 5-LED system can give aslightly higher contrast of 6.4%, but also a higher CII of 3.

Any single simulation will not account for or control for all thepossible contrast effects that can arise in daily experience.Ultimately, the near-infinite number of environments with their uniquegeometries, object arrangements, and interplay with outdoor lightingprovide for a near-infinite range of lighting situations. Observervariability adds an additional confounding factor.

While we have used example color appearance models to assess dynamiclighting changes in determining appropriate light modulation models,other color appearance models may be used. For example, the recent CIEcolor appearance model, CIECAM02, could be used, although environmentalvariability may limit the usefulness of that model. CIECAM02, forexample, provides a streamlined and effective means to describe colorappearance with respect to scene context, but would require knownbackground and surround conditions.

Other factors may also be applied when determining an appropriate lightmodulation model for producing dynamic light. Mesopic visual responsemay be considered, for example. Mesopic visual responses become relevantat lower lighting levels. The melanopsin contrast optimization algorithmdescribed above does not consider rod responses whatsoever, as rods arelikely saturated or nearly saturated under our dynamic lighting.Utilizing a more complicated model that takes into account mesopicvision could be achieved using the Hunt (R. W. G. Hunt: The Reproductionof Colour (Fountain Pr., England, 1995) 5th ed., Chap. 31, p. 705)model, for example. Adding rod response to the present models would addto the list of constraints and may reduce melanopsin contrast. The modelcould use even further, more advanced illuminant designs where the colorcoordinates of the illuminant itself are allowed to vary. The motivationwould be to reduce the just noticeable differences (JNDs) in colorsample tests to below threshold. A consideration with such models isthat a favorable shift in JND for one color may be offset by unfavorableshifting for other colors. There are numerous contrast phenomena, whichcould take place based on the arbitrary arrangements of objects, such assimultaneous contrast and crispening effects. Ultimately, quantifyingtrue melanopsin contrast would be best achieved using an accurateassessment of contrast not only from the direct illuminant itself, butthe summation of all reflections in a given environment. Therefore themodulation model could be adapted to consider such reflection effects,partly or in total. However, generally speaking some self-restraint fromover-modeling allows for conceptual and computational simplicity, whilebeing no less accurate on balance than a highly refined simulation whenit comes to general modeling.

While these additional factors can be implemented in producing the lightmodulation models herein, in exemplary embodiments, the broader approachdescribed above is used to produce dynamic light (i.e., dynamicillumination). As discussed herein, we observed general trends throughstatistical analysis of the data.

We observed that more LEDs will provide more contrast, but more LEDs canlead to more instability in color appearance as a high proportion ofsimulation states, causing an increase in CII as well as larger changesin CRI and CQS. CII, as well as CRI, CQS, and other light qualitymetrics and indices, can be used to provide further constraints inselecting the light modulation modes that provide the best utility. Inthe case of CII, constraining below a certain value for test colorsample and/or environmental objects calculations may be desirable. Inthe case of light quality indices, a limit in the change in index valuebetween the light modulation modes may be desirable.

Therefore, in some examples, we counteract the instability by decreasingthe independence of the LED channels by broadening the spectral width ofeach LED. Surprisingly, spectral broadening does not impact the contrastvalues significantly. Programming a narrow cone-change tolerance range(say ±5%) to TCS into the algorithm limits permitted contrast values tolevels below those which result from spectral broadening—up to FWHMvalues as high 50 nm. The benefit of large spectral width wasdemonstrated in our general lighting example. In practice, large FWHMcan be obtained from LED chips of relatively low quality. If needed,phosphors can be incorporated into the lighting design.

In exemplary embodiments, only three metrics may be assessed: melanopsincontrast, color fidelity and/or quality, and constancy of sceneappearance. Using four or more independently controlled LED channels, anoptimization model has been presented to maximize melanopsin contrastwhile maintaining good quality for color rendering and colortemperature. For example, a moderate melanopsin contrast of 5% can beachieved with excellent CRI and CII. Such a light source could replaceexisting interior lighting to improve well-being and productivity.

As seen from the considerable spread in outputs, even when correlationsare relatively high, our method benefits from a large number ofiterations from which one can cherry-pick the combination of systemtraits providing the best contrast, constancy, and color rendering.Furthermore, the methods herein may control for nonlinear outputs suchas CRI and CII in addition to contrast during 7. For example, thetechniques herein may use null space analysis and subspace optimization,using a model to conduct calculus of several variables and find extremawith respect to variables. The techniques may use manifold analysis ofthe hyperspace of x,y-doublets which overlap in chromaticity space.

The dynamic (modulated) lighting described herein could prove especiallyadvantageous in settings with a general lack of sunlight, such assettlements in and around the Arctic Circle where winters can be almostentirely devoid of light, and inside submarines. Dynamic lighting wouldalso be beneficial at work and school where alertness and productivityis key. Environments such as factories could rely on such lighting toboost productivity or maintain alertness in order to minimize workplaceinjury.

We have empirical data suggesting that the melanopsin-specific dynamiclight enhances alertness and cognitive performance in human subjects.FIG. 11 illustrates human EEG recordings obtained using the 5-channellight source. To generate a melanopsin-selective oscillation, thecombined emission spectrum alternated smoothly between a state thatweakly stimulates melanopsin (“min” in FIG. 11) and another thatstimulates melanopsin more strongly (“max”). Both states excite conesalmost equally, and fully saturate rods; thus, the oscillation betweenthe two states specifically targeted melanopsin. The resulting dynamiclight had a comfortable warm white hue and appeared remarkably constantto the observer. These EEG data suggest that this subconsciouslyflickering light increases alertness significantly more than steadylight. In the test of FIG. 11, we objectively quantified the subjects'alertness by measuring EEG frequencies in the low alpha range, asresearchers have found that a decrease in power within this range iscorrelated with an increase in alertness. The slowly flickering stimuli(0.01 Hz and 0.1 Hz) tended to reduce low-alpha signals more than theother stimuli, including the “max” steady light which emitted morephotons than the flickers, suggesting that melanopsin-targetedflickering light promotes alertness better than steady light. In anotherhuman study, summarized in FIG. 12, we used a computer-based test toevaluate cognitive performance under either the 5-LED light delivering amelanopsin-selective oscillation, or the 5-LED light held steady eitherat the minimum-melanopsin state or the maximum-melanopsin state. Resultsshowed that under the melanopsin-selective oscillating light, thesubjects completed the cognitive test with shorter reaction times, alower distractability, and lower error rates.

FIG. 13 illustrates a processing system 2 for generating lightmodulation models and controlling light output to produce dynamic light,in accordance with examples described above. Melanopsin contrast data 12and color fidelity and quality data 14 are provided to a lightmodulation model generator 4, formed of a processing device having oneor more processors executing non-transitory instructions stored on oneor more processor readable memories also within the processing device.Optionally, light source data 16, such as the type of light source (LEDor other), the total number of LEDs available for using in the model,the color output of the LEDs, a color temperature data, includingenvironmental color temperatures for the ambient space to beilluminated, may be provided to the processing device. The processingdevice includes a melanopsin contrast optimizer 6, a color fidelityoptimizer 8, and a light and lighting environment assessment module 10.The processing devices generate a light modulation model 18 which may bea set of modulation instructions in an executable format, whetherdigital data or analog data, that will be used to modulate light fromthe light source.

FIG. 14 illustrates an example implementation of the generated lightmodel 20 in an LED light formed of an LED array 26. Here, LED arrayrefers to any light source having one or more LEDs. A power source 22provides light control signals to a dynamic lighting modulator 24 thatstores the light model and that provides modulation instruction signalsto the LED array 26 to modulate the light in accordance with thatdetermined through the techniques described herein. Optionally, thelight source may include a communication interface 28 coupled to thedynamic lighting modulator 24 to allow for communication with a separatecontrol device 30, such as a handheld computer, for modifying lightmodulation model data stored in the dynamic lighting modulator 24.

FIG. 15 is an example of a flat panel display device 30 having two LEDs32 electrically connected to a light controller 34 providing modulatinglight signal controls to the LEDs, and with a diffuser panel 36 forevenly emitting light.

FIG. 16 is an example of an Edisonian lighting configuration 40 in whichtwo LEDs 42 electrically connected to a light controller 44 providingmodulating light signal controls to the LEDs, are housed within a lightbulb shaped housing 46 and in which a diffuser panel 48 is shown.

FIG. 17 illustrates an exemplary method 100 of adapting a pulsed lightfor general illumination. At box 102, the method 100 comprises providinga plurality of LED channels each generating light, the LED channelsincluding at least four distinctly colored LEDs. At box 104, the method100 comprises setting a first light mode at a first spectrum tomaximally stimulate melanopsin responsiveness of a subject, the firstspectrum being formed by light from the at least four distinctly coloredLEDs, the first light mode having a light intensity that maximizesmelanopsin contrast responsiveness and having a blue light intensity, ared light intensity, and/or a green light intensity that define a colortemperature and brightness of the first light mode. At box 106, themethod 100 comprises setting a second light mode at a second spectrum tomore weakly stimulate melanopsin responsiveness of the subject comparedto the first light mode, the second spectrum being formed by light fromthe at least four distinctly colored LEDs, the second light mode havinga light intensity that more weakly stimulates melanopsin responsivenessand having a blue light intensity, red light intensity, and/or a greenlight intensity that define a color temperature and brightness of thesecond light mode. At box 108, the method 100 comprises setting thecolor temperature and brightness of the first light mode to match thecolor temperature and brightness of the second light mode. At box 110,the method 100 comprises modulating between the first light mode and thesecond light mode to stimulate the subject while maintaining anoptimized melanopsin contrast between the first light mode and thesecond light mode.

Maintaining an optimized melanopsin contrast between the first lightmode and the second light mode may include maximizing the melanopsincontrast between the first light mode and the second light mode. Each ofthe first light mode and the second light mode is characterized by acorrelated color temperature (CCT) and brightness, and the method mayfurther include iteratively setting the first light mode and the secondlight mode over a CCT from 3000 to 11000 K in intervals, and modulatingbetween the first light mode and the second light mode each iteration.The method may further include determining whether the first spectrumand the second spectrum induce a change in cone response from test colorsamples within a maximum acceptable cone response change range. Themethod may further include determining whether the first spectrum andthe second spectrum induce a change in cone response from test colorsamples within a maximum acceptable cone response change range.

Additionally, the method may include determining whether the firstspectrum and the second spectrum induce a change in cone response fromtest color samples within a maximum acceptable cone response changerange. The method may include configuring the first spectrum and thesecond spectrum to be cone metamers by applying a mathematicaloptimization algorithm with constraints. If the first spectrum and thesecond spectrum induce a change in cone response from test colorsamples, the method may include calculating a color inconstancy index(CII) of the first spectrum with respect to the second spectrum and, ifthe value of the CII between the first spectrum and the second spectrumis greater than a maximum acceptable CII value, adjusting the firstspectrum and/or the second spectrum until the value of the CII given thefirst spectrum and the second spectrum is within an acceptable CIIvalue. Similarly, if the first spectrum and the second spectrum induce achange in cone response from test color samples, the method may includecalculating light quality indices of the first spectrum and of thesecond spectrum and calculating a difference between the light qualityindices of the first spectrum and the second spectrum and, if thedifference is greater than a maximum acceptable light quality indexchange, adjusting the first spectrum and/or the second spectrum untilthe difference is less than or equal to maximum acceptable light qualityindex change. Calculating light quality indices may include calculatinga Color Rendering Index (CRI) and/or a Color Quality Scale (CQS) and/ora Michelson contrast and/or a Weber contrast.

The techniques herein may be used in any number of lightingconfigurations and light applications. For example, the modulated lighttechniques may be used for therapeutic lighting, in which light ismodulated to a desired amount having the largest therapeutic effect on asubject or group of subjects. Subjects may be provided a series ofdifferent modulated light conditions, for example, at differentwavelengths and using different combinations of different-wavelengthemitting LEDs, and different numbers of LEDs. From there, an optimumtherapeutic modulated light model may be developed for use with thesubject. In some examples, that light model may be programmed intoautomated lighting systems, such as wirelessly-enabled lightingsolutions in the home, whereby the model can be applied to the lightingwhen the presence of the subject has been detected. An example of suchtherapeutic lighting could be deployed for seasonal affective disorder(SAD).

The lighting module can be one that affects the lighting in the home,work space, commercial space or other on an ongoing basis or atparticular times of the year, as with SAD.

The light modulation techniques herein may be incorporated into displaysby modulating light, and more particularly part of the display screenimage or even the overall color space of a display, to increase theresponsiveness of a subject. Indeed, with a control display, such ascomputer screen or handheld device screen, tests can be given tosubjects while simultaneously adjusting modulating lighting conditionsto assess optimum conditions for a subject. Those tests could beproductivity tests, alertness tests, drowsiness tests, response timetests, or any number of other measurable metrics of brain activity thatmight be affected by lighting conditions.

In yet other examples, the techniques may be used for overall lightmixing, such as use in fiber optics for mixing of different LED light,for display or data communication purposes.

Throughout this specification, plural instances may implementcomponents, operations, or structures described as a single instance.Although individual operations of one or more methods are illustratedand described as separate operations, one or more of the individualoperations may be performed concurrently, and nothing requires that theoperations be performed in the order illustrated. Structures andfunctionality presented as separate components in example configurationsmay be implemented as a combined structure or component. Similarly,structures and functionality presented as a single component may beimplemented as separate components. These and other variations,modifications, additions, and improvements fall within the scope of thesubject matter herein.

Additionally, certain embodiments are described herein as includinglogic or a number of routines, subroutines, applications, orinstructions. These may constitute either software (e.g., code embodiedon a machine-readable medium or in a transmission signal) or hardware.In hardware, the routines, etc., are tangible units capable ofperforming certain operations and may be configured or arranged in acertain manner. In example embodiments, one or more computer systems(e.g., a standalone, client or server computer system) or one or morehardware modules of a computer system (e.g., a processor or a group ofprocessors) may be configured by software (e.g., an application orapplication portion) as a hardware module that operates to performcertain operations as described herein.

In various embodiments, a hardware module may be implementedmechanically or electronically. For example, a hardware module maycomprise dedicated circuitry or logic that is permanently configured(e.g., as a special-purpose processor, such as a field programmable gatearray (FPGA) or an application-specific integrated circuit (ASIC)) toperform certain operations. A hardware module may also compriseprogrammable logic or circuitry (e.g., as encompassed within ageneral-purpose processor or other programmable processor) that istemporarily configured by software to perform certain operations. Itwill be appreciated that the decision to implement a hardware modulemechanically, in dedicated and permanently configured circuitry, or intemporarily configured circuitry (e.g., configured by software) may bedriven by cost and time considerations.

Accordingly, the term “hardware module” should be understood toencompass a tangible entity, be that an entity that is physicallyconstructed, permanently configured (e.g., hardwired), or temporarilyconfigured (e.g., programmed) to operate in a certain manner or toperform certain operations described herein. Considering embodiments inwhich hardware modules are temporarily configured (e.g., programmed),each of the hardware modules need not be configured or instantiated atany one instance in time. For example, where the hardware modulescomprise a general-purpose processor configured using software, thegeneral-purpose processor may be configured as respective differenthardware modules at different times. Software may accordingly configurea processor, for example, to constitute a particular hardware module atone instance of time and to constitute a different hardware module at adifferent instance of time.

Hardware modules can provide information to, and receive informationfrom, other hardware modules. Accordingly, the described hardwaremodules may be regarded as being communicatively coupled. Where multipleof such hardware modules exist contemporaneously, communications may beachieved through signal transmission (e.g., over appropriate circuitsand buses) that connects the hardware modules. In embodiments in whichmultiple hardware modules are configured or instantiated at differenttimes, communications between such hardware modules may be achieved, forexample, through the storage and retrieval of information in memorystructures to which the multiple hardware modules have access. Forexample, one hardware module may perform an operation and store theoutput of that operation in a memory device to which it iscommunicatively coupled. A further hardware module may then, at a latertime, access the memory device to retrieve and process the storedoutput. Hardware modules may also initiate communications with input oroutput devices, and can operate on a resource (e.g., a collection ofinformation).

The various operations of the example methods described herein may beperformed, at least partially, by one or more processors that aretemporarily configured (e.g., by software) or that are permanentlyconfigured to perform the relevant operations. Whether temporarily orpermanently configured, such processors may constituteprocessor-implemented modules that operate to perform one or moreoperations or functions. The modules referred to herein may, in someexample embodiments, comprise processor-implemented modules.

Similarly, the methods or routines described herein may be at leastpartially processor-implemented. For example, at least some of theoperations of a method may be performed by one or more processors or byprocessor-implemented hardware modules. The performance of certain ofthe operations may be distributed among the one or more processors, notonly residing within a single machine (having different processingabilities), but also deployed across a number of machines. In someexample embodiments, the processors may be located in a single location(e.g., deployed in the field, in an office environment, or as part of aserver farm), while in other embodiments the processors may bedistributed across a number of locations.

Unless specifically stated otherwise, discussions herein using wordssuch as “processing,” “computing,” “calculating,” “determining,”“presenting,” “displaying,” or the like may refer to actions orprocesses on a GPU thread that manipulates or transforms datarepresented as physical (e.g., electronic, magnetic, or optical)quantities within one or more memories (e.g., volatile memory,non-volatile memory, or a combination thereof), registers, or othermachine components that receive, store, transmit, or displayinformation.

As used herein any reference to “one embodiment” or “an embodiment”means that a particular element, feature, structure, or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment.

Some embodiments may be described using the expression “coupled” and“connected” along with their derivatives. For example, some embodimentsmay be described using the term “coupled” to indicate that two or moreelements are in direct physical or electrical contact. The term“coupled,” however, may also mean that two or more elements are not indirect contact with each other, but yet still co-operate or interactwith each other. The embodiments are not limited in this context.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

In addition, use of the “a” or “an” are employed to describe elementsand components of the embodiments herein. This is done merely forconvenience and to give a general sense of the description. Thisdescription, and the claims that follow, should be read to include oneor at least one and the singular also includes the plural unless it isobvious that it is meant otherwise.

This detailed description is to be construed as an example only and doesnot describe every possible embodiment, as describing every possibleembodiment would be impractical, if not impossible. One could implementnumerous alternate embodiments, using either current technology ortechnology developed after the filing date of this application.

What is claimed:
 1. A method of adapting a pulsed light for generalillumination, the method comprising: providing a plurality of LEDchannels each generating light, the LED channels including at least fourdistinctly colored LEDs; setting a first light mode at a first spectrumto maximally stimulate melanopsin responsiveness of a subject, the firstspectrum being formed by light from the at least four distinctly coloredLEDs, the first light mode having a light intensity that maximizesmelanopsin contrast responsiveness and having a blue light intensity, ared light intensity, and/or a green light intensity that define a colortemperature and brightness of the first light mode; setting a secondlight mode at a second spectrum to more weakly stimulate melanopsinresponsiveness of the subject compared to the first light mode, thesecond spectrum being formed by light from the at least four distinctlycolored LEDs, the second light mode having a light intensity that moreweakly stimulates melanopsin responsiveness and having a blue lightintensity, red light intensity, and/or a green light intensity thatdefine a color temperature and brightness of the second light mode;setting the color temperature and brightness of the first light mode tomatch the color temperature and brightness of the second light mode; andmodulating between the first light mode and the second light mode tostimulate the subject while maintaining an optimized melanopsin contrastbetween the first light mode and the second light mode, iterativelysetting a correlated color temperature (CCT) value of the first lightmode and the second light mode from 3000 to 11000K in intervals and, foreach CCT value, ensuring the color temperature and brightness of thefirst light mode match the color temperature and brightness of thesecond light mode and the optimized melanopsin contrast between thefirst light mode and the second light mode is maintained, andconfiguring the first spectrum and the second spectrum to be conemetamers by searching, by a processor and during development of a lightmodulation model, a set of possible first spectrums and a set ofpossible second spectrums to find a pair of spectra that generate theleast shift in cone excitation from standardized test color samples. 2.The method of claim 1, wherein the optimized melanopsin contrast betweenthe first light mode and the second light mode is the maximum melanopsincontrast between the first light mode and the second light mode.
 3. Themethod of claim 1, wherein iteratively setting the correlated colortemperature (CCT) value from 3000 to 11000K occurs in 100 K intervals.4. The method of claim 3, the method further comprising: determining, bya processor, whether the first spectrum and the second spectrum induce achange in cone response from test color samples within a maximumacceptable cone response change range.
 5. The method of claim 1, themethod further comprising: when the first spectrum and the secondspectrum induce a change in cone response from test color samples,calculating a color inconstancy index (CII) of the first spectrum withrespect to the second spectrum; and when the value of the CII betweenthe first spectrum and the second spectrum is greater than a maximumacceptable CII value, adjusting the first spectrum and/or the secondspectrum until the value of the CII given the first spectrum and thesecond spectrum is within an acceptable CII value.
 6. The method ofclaim 1, when the first spectrum and the second spectrum induce a changein cone response from test color samples, calculating light qualityindices of the first spectrum and of the second spectrum and calculatinga difference between the light quality indices of the first spectrum andthe second spectrum; and when the difference is greater than a maximumacceptable light quality index change, adjusting the first spectrumand/or the second spectrum until the difference is less than or equal tomaximum acceptable light quality index change.
 7. The method of claim 6,wherein calculating light quality indices includes calculating a ColorRendering Index (CRI) and/or a Color Quality Scale (CQS) and/or aMichelson contrast and/or a Weber contrast.